Conventional semiconductor manufacturing processes may cause drifting to occur, and the drifting in the semiconductor processes may result in a change of parameters (for example, impedance, inductance and resistance) of various electronic elements in integrated circuits. In communication systems, the transmitter and the receiver must strictly match each other in impedance, and lack thereof may result in signal distortion or signal loss. While resistances may be modified in the prior art by fine-tuning, and the occurrence of drifting may be reduced by process control, the former would increase test times and costs, and the latter would increase costs associated with integrated circuits.